Statistical model of crop losses caused by maize stem borers (Lepidoptera: Noctuidae, Pyralidae) in Cote d'Ivoire
1996
Moyal, P.
Six experiments were conducted in the savanna and forest areas of Cote d'Ivoire to study the influence of stem borers on maize crop yield components and production. Statistical models showed the effect of the oldest preimaginal instars of 2 stem borers, Eldana saccharina Walker (Pyralidae) and Busseola fusca (Fuller) (Noctuidae). Plant destruction was mainly caused by early attack of B. fusca. Attack by both borers on or about the 60th d after emergence induced plant sterility. Stem borers had no direct effect on number of grains per cob-carrying plant: the level of this yield component was set according to the level of the previously determined components through a compensation phenomenon. The test yield component, average weight of grain, decreased with attack by E. saccharina occurring on or about the 80th d after emergence. Effects of borer aggregation, maize variety, and maize streak virus incidence were studied. The statistical model of crop loss, which explains 81.7% of the variation in yield, was validated from the results of 3 trials that were not included in the regression analysis. It enables one to intimate accurately crop losses in most of Cote d'Ivoire with only 2 samplings during the growing season, on the 40th and 80th d after emergence.
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